In many applications of construction technology, tools are used, which are tipped with cutters, which contain diamond particles in order to improve their abrasive properties. For preparing boreholes or openings of larger diameter, hollow drill crowns are used, equipped at their front ends with cutting segments. Wall saws and cutting-off wheels for cutting concrete, stone or ceramic are tipped at their periphery with cutting segments. Furthermore, grinding disks are also known for working hard surfaces edged at their flat side with cutters containing diamond particles. The abrasive cutters consist essentially of diamond particles, preferably diamond crystals, embedded in a metallic matrix and have a more or less regular shape. The cutting segments, with which the hollow drill crowns or wall saw blades and cutting-off blades are tipped, have a larger volume and a regular shape.
To produce the abrasive cutters or the larger cutting segments, diamond particles are mixed with a metal powder and optionally further components, such as hard material particles. The mixture of diamond particles, metal powder and optionally further components either is sintered directly and baked together into a cake-like mass, which is broken up once again into small parts in a subsequent step. After the broken parts are screened, the usable screen fractions with the suitable particle sizes are used for coating grinding disks and the like. For producing cutting segments, such as, hollow drill crowns, wall saws or cutting-off wheels, the mixture of diamond particles, metal powder and optionally further components, to begin with, is pressed into the desired shape. The resulting green compact is finally sintered, in order to combine the compressed mixture permanently.
In the case of this known method, it happens, particularly at high concentrations of diamond particles, that the diamond particles within the metal powder, acting as binder, lie directly in contact with one another. The bonding at such diamond-diamond contacts is only weak and can lead to weaknesses within the abrasive cutter. Some improvement in the situation occurs if the diamond particles are coated with a metal layer before they are mixed with the metal powder. However, only relatively thin layers can be deposited at the surface of the diamond particles with the known coating techniques. The deposition usually is accomplished by galvanic means, and layers up to about 5 .mu.m can be achieved. CVD (chemical vapor deposition) or PVD (physical vapor deposition) techniques are relatively cumbersome and expensive. They are used sometimes in order to bond larger diamond particles better into a polymer matrix. They are generally not suitable for improving the bonding in a metallic matrix. Layer thicknesses, achievable with these coating techniques, generally are also less than those achievable with galvanic methods.